微地震信号频率特性分析

Analysis of frequency characteristics of micro-seismic signals

微地震信号的频率可影响地震资料的分辨率等,是一种重要特征参数。本文分析了微地震信号的频率特性,研究了信号在传播过程中的三个影响因素:震源破裂尺度、传播介质的黏弹性效应和接收仪器的响应频带等。结果表明:随着微地震信号传播距离的增大,信号频率降低,当传播到一定距离时,信号频率基本不再变化;完全弹性介质中地震波主频不变,但在黏弹性介质中,随着传播距离的增大,地震波能量急剧减小、主频明显变低;地震信号在传播过程中其主频呈总体下降趋势,但在层位界面处主频有一个增大的转折。

Frequency of micro-seismic signals is a very important characteristic parameter which may affect seismic data resolution.In this paper,frequency characteristics of micro-seismic signals are analyzed such as source rupture scale,viscoelastic effect of medium,and frequency bandwidth response of recorders in the signal propagation process.The following observations are obtained from our work:A.Signal frequency decreases with propagation distance increase.When the propagation distance increases to a certain degree,the signal frequency become unchanged;B.The dominant frequency does not change in full elastic medium,but it decreases with propagation distance increase in viscoelastic medium,and seismic energy decreases too with the propagation distance;C.The dominant frequency decreases gradually during signal propagation process,but it decreases suddenly when crossing an interface.